ref: f2573a061174eedf0ce1e46a94e963ba275615ba
parent: 29a7965fd14f0a142965067e04f6b8e4ba354d3e
author: Werner Lemberg <[email protected]>
date: Fri Aug 5 05:07:21 EDT 2011
[truetype] Fix some comments in the bytecode interpreter. Thanks to Greg Hitchcock!
--- a/src/truetype/ttinterp.c
+++ b/src/truetype/ttinterp.c
@@ -16,6 +16,10 @@
/***************************************************************************/
+/* Greg Hitchcock from Microsoft has helped a lot in resolving unclear */
+/* issues; many thanks! */
+
+
#include <ft2build.h>
#include FT_INTERNAL_DEBUG_H
#include FT_INTERNAL_CALC_H
@@ -664,9 +668,9 @@
FT_Int i;
- /* XXXX: Will probably disappear soon with all the code range */
- /* management, which is now rather obsolete. */
- /* */
+ /* XXX: Will probably disappear soon with all the code range */
+ /* management, which is now rather obsolete. */
+ /* */
size->num_function_defs = exec->numFDefs;
size->num_instruction_defs = exec->numIDefs;
@@ -5095,8 +5099,8 @@
CUR_Func_move( &CUR.zp2, L, args[1] - K );
- /* not part of the specs, but here for safety */
-
+ /* UNDOCUMENTED! The MS rasterizer does that with */
+ /* twilight points (confirmed by Greg Hitchcock) */
if ( CUR.GS.gep2 == 0 )
CUR.zp2.org[L] = CUR.zp2.cur[L];
}
@@ -5920,9 +5924,9 @@
return;
}
- /* XXX: UNDOCUMENTED! behaviour */
- if ( CUR.GS.gep1 == 0 ) /* if the point that is to be moved */
- /* is in twilight zone */
+ /* UNDOCUMENTED! The MS rasterizer does that with */
+ /* twilight points (confirmed by Greg Hitchcock) */
+ if ( CUR.GS.gep1 == 0 )
{CUR.zp1.org[point] = CUR.zp0.org[CUR.GS.rp0];
CUR_Func_move_orig( &CUR.zp1, point, args[1] );
@@ -5965,8 +5969,6 @@
return;
}
- /* XXX: Is there some undocumented feature while in the */
- /* twilight zone? ? */
if ( ( CUR.opcode & 1 ) != 0 )
{cur_dist = CUR_fast_project( &CUR.zp0.cur[point] );
@@ -6009,34 +6011,34 @@
goto Fail;
}
- /* XXX: UNDOCUMENTED! */
- /* */
- /* The behaviour of an MIAP instruction is quite */
- /* different when used in the twilight zone. */
- /* */
- /* First, no control value cut-in test is performed */
- /* as it would fail anyway. Second, the original */
- /* point, i.e. (org_x,org_y) of zp0.point, is set */
- /* to the absolute, unrounded distance found in */
- /* the CVT. */
- /* */
- /* This is used in the CVT programs of the Microsoft */
- /* fonts Arial, Times, etc., in order to re-adjust */
- /* some key font heights. It allows the use of the */
- /* IP instruction in the twilight zone, which */
- /* otherwise would be `illegal' according to the */
- /* specification. */
- /* */
- /* We implement it with a special sequence for the */
- /* twilight zone. This is a bad hack, but it seems */
- /* to work. */
+ /* UNDOCUMENTED! */
+ /* */
+ /* The behaviour of an MIAP instruction is quite different when used */
+ /* in the twilight zone. */
+ /* */
+ /* First, no control value cut-in test is performed as it would fail */
+ /* anyway. Second, the original point, i.e. (org_x,org_y) of */
+ /* zp0.point, is set to the absolute, unrounded distance found in the */
+ /* CVT. */
+ /* */
+ /* This is used in the CVT programs of the Microsoft fonts Arial, */
+ /* Times, etc., in order to re-adjust some key font heights. It */
+ /* allows the use of the IP instruction in the twilight zone, which */
+ /* otherwise would be invalid according to the specification. */
+ /* */
+ /* We implement it with a special sequence for the twilight zone. */
+ /* This is a bad hack, but it seems to work. */
+ /* */
+ /* Confirmed by Greg Hitchcock. */
distance = CUR_Func_read_cvt( cvtEntry );
if ( CUR.GS.gep0 == 0 ) /* If in twilight zone */
{- CUR.zp0.org[point].x = TT_MulFix14( (FT_UInt32)distance, CUR.GS.freeVector.x );
- CUR.zp0.org[point].y = TT_MulFix14( (FT_UInt32)distance, CUR.GS.freeVector.y ),
+ CUR.zp0.org[point].x = TT_MulFix14( (FT_UInt32)distance,
+ CUR.GS.freeVector.x );
+ CUR.zp0.org[point].y = TT_MulFix14( (FT_UInt32)distance,
+ CUR.GS.freeVector.y ),
CUR.zp0.cur[point] = CUR.zp0.org[point];
}
@@ -6220,19 +6222,17 @@
cvt_dist = -CUR.GS.single_width_value;
}
- /* XXX: UNDOCUMENTED! -- twilight zone */
-
+ /* UNDOCUMENTED! The MS rasterizer does that with */
+ /* twilight points (confirmed by Greg Hitchcock) */
if ( CUR.GS.gep1 == 0 )
{CUR.zp1.org[point].x = CUR.zp0.org[CUR.GS.rp0].x +
TT_MulFix14( (FT_UInt32)cvt_dist,
CUR.GS.freeVector.x );
-
CUR.zp1.org[point].y = CUR.zp0.org[CUR.GS.rp0].y +
TT_MulFix14( (FT_UInt32)cvt_dist,
CUR.GS.freeVector.y );
-
- CUR.zp1.cur[point] = CUR.zp0.cur[point];
+ CUR.zp1.cur[point] = CUR.zp0.cur[point];
}
org_dist = CUR_Func_dualproj( &CUR.zp1.org[point],